Power Liftgate System

Some vehicles are equipped with an automatic opening and dosing power liftgate. The power lift-gate system is a complex system consisting of many components. Refer to the following list for component reference:

Drive Unit Components
- Liftgate Motor Clutch
- Channel, Bracket, Full Open Switch Optical Sensor Link Rod
- Rack and Yoke Assembly
- Power Liftgate System Components

Power Latch and Actuator
- Liftgate Power Module
- Pinch Sensor
- Overhead Console and Key Fob Command Switches
- Chime/Thermistor Assembly

The power liftgate system utilizes its own liftgate control module. This power liftgate module contains all the solid state hardware and software used to control the power liftgate system. For specific component information refer to the individual component descriptions later.

Safety is of the utmost concern with the power lift-gate system. Software technology has enabled the power liftgate module to detect resistance to liftgate travel. This allows the power liftgate module to control liftgate direction anytime an obstruction is detected. The power liftgate can be operated manually using the liftgate outside handle switch.

The power liftgate module communicates on the Programmable Communication Interface (PCI) Bus Circuit. Therefore, the power liftgate module can generate and store its own Diagnostic Trouble Codes (DTC's). The Body Control Module (BCM) sends and receives messages to the power liftgate control module via the PCI bus circuit. A diagnostic scan tool, such as the DRB III(R) is used to read and trouble-shoot these Diagnostic Trouble Codes. Refer to the Body Diagnostic Information for a list of diagnostic procedures.

Battery voltage is supplied to the power liftgate system through a 40 amp fuse, located in the Integrated Power Module (IPM) assembly. With the push of a power liftgate open/close command switch (key fob or overhead console mounted), a signal is sent out on the PCI Data Bus circuit. This signal is detected at the Body Control Module (BCM). The BCM then adds system status and sends a signal out on the PCI Data Bus circuit to the power liftgate control module. The power liftgate control module then interprets the information to confirm safety requirements are met before applying power to the power liftgate motor to start a power cycle.

During a power liftgate open or close cycle, if the power liftgate control module detects sufficient resistance to liftgate travel, such as an obstruction in the liftgate's path. The control module will immediately stop liftgate movement and reverse the direction of travel to the full open or closed position. The ability for the power liftgate control module to detect resistance to liftgate travel is accomplished by the optical and pinch sensors.

The power liftgate control module has the ability to relearn. After 8 miles have been recorded on the odometer, anytime the liftgate is fully opened and fully closed using the automatic system, the module will learn from its cycle. If a replacement power lift-gate component is installed or a liftgate adjustment is made, the module will relearn the effort and/or time required to open or close the liftgate. This learn cycle can be performed with a Diagnostic Scan Tool, such as the DRB III(R) or with a complete cycle of the liftgate, using either one of the command switches. Refer to Standard Procedures for detailed instructions.

For a complete wiring schematic of the power lift-gate system, refer to the Wiring section of this manual. For system operation instructions refer to the vehicles owner manual. Refer to the Body Section of this manual for additional information on liftgate components such as the prop rods, hinges, door alignment and striker alignment.

The power liftgate system is designed with a number of system inhibitors. These inhibitors are necessary for safety and/or feasibility of the power liftgate system. Refer to power liftgate system inhibitors noted below:

POWER LIFTGATE SYSTEM INHIBITORS
- The Power Liftgate module will inhibit operation of the power liftgate in extreme temperatures. These temperatures will be approximately -22° F (-33° C) and 149° F (65° C). A chime/thermister assembly in the rear light bar assembly monitors the outside temperature.
- The vehicle's transmission must be in park or neutral for the power liftgate to operate.
- The vehicle's speed must be zero for the power liftgate to operate.
- The vehicle's electrical system voltage must be within specification for the power liftgate system to operate. A low-voltage cut-off is built into the power liftgate system to prevent the vehicle's battery from discharging to the point were the vehicle cannot be operated.
- If the vehicle's ignition switch is in the "START" position, the power liftgate will pause.
- If multiple obstacles are detected during the same power open or close cycle, the liftgate will temporarily go into full manual operation.
- If severe Diagnostic Trouble Codes (DTC's) are stored in the power liftgate control module the system may not operate.